Patent Literature 1 discloses a hybrid focus detection unit that includes a focus detection unit of a phase difference detection method (simply referred to as a “phase difference AF” hereinafter), and a focus detection unit of a contrast detection method (simply referred to as a “TVAF” hereinafter). Patent Literature 2 discloses a phase difference detection (image pickup surface phase difference AF (simply referred to as a “SAF” hereinafter) function by providing an image pickup device with an imaging pixel and a focus detecting pixel, and a pupil splitting unit. Patent Literature 3 discloses a phase difference AF using a secondary imaging optical system.
Other prior art include Patent Literatures 4 and 5.